use std::collections::HashMap;
use std::sync::atomic::Ordering;

use etcd_client::PutOptions;
use tokio_stream::StreamExt;

use crate::error::{AppError, AppResult};

use super::EtcdRegistry;
use super::EtcdRegistryInner;
use super::types::ServiceInstance;

impl EtcdRegistry {
    pub async fn register_self(&self, service_name: &str) -> AppResult<()> {
        let ttl = self.inner.config.etcd_lease_ttl()?;
        let listen_addr = self.inner.config.rpc_self_listen_addr()?;

        let instance_id = uuid::Uuid::now_v7().to_string();
        let key = format!(
            "{}services/{service_name}/{instance_id}",
            self.inner.key_prefix
        );

        let instance = ServiceInstance {
            addr: listen_addr.clone(),
            metadata: HashMap::new(),
        };
        let value = serde_json::to_string(&instance)?;

        let lease_resp = {
            let mut client = self.inner.client.lock().await;
            client
                .lease_grant(ttl as i64, None)
                .await
                .map_err(|e| AppError::Config(format!("etcd lease_grant failed: {e}")))?
        };
        let lease_id = lease_resp.id();
        self.inner.lease_id.store(lease_id, Ordering::SeqCst);

        {
            let mut client = self.inner.client.lock().await;
            let opts = PutOptions::new().with_lease(lease_id);
            client
                .put(key.clone(), value, Some(opts))
                .await
                .map_err(|e| AppError::Config(format!("etcd put failed: {e}")))?;
        }

        tracing::info!(
            service = service_name,
            addr = listen_addr.as_str(),
            lease_id = lease_id,
            "registered self in etcd"
        );

        self.spawn_keep_alive(lease_id, key);

        Ok(())
    }

    fn spawn_keep_alive(&self, lease_id: i64, key: String) {
        let inner = self.inner.clone();
        let interval = self.inner.config.etcd_keep_alive_interval().unwrap_or(10);

        tokio::spawn(async move {
            loop {
                Self::run_keep_alive_stream(&inner, lease_id).await;
                tokio::time::sleep(std::time::Duration::from_secs(interval)).await;
                Self::renew_lease_and_reregister(&inner, lease_id, &key).await;
            }
        });
    }
}

impl EtcdRegistry {
    async fn run_keep_alive_stream(
        inner: &std::sync::Arc<EtcdRegistryInner>,
        lease_id: i64,
    ) {
        let result = {
            let mut client = inner.client.lock().await;
            client.lease_keep_alive(lease_id).await
        };

        match result {
            Ok((_keeper, mut stream)) => {
                while let Some(resp) = stream.next().await {
                    if let Err(e) = resp {
                        tracing::warn!(lease_id = lease_id, error = %e, "keep-alive stream error");
                        break;
                    }
                }
            }
            Err(e) => {
                tracing::warn!(lease_id = lease_id, error = %e, "keep-alive failed");
            }
        }
    }

    async fn renew_lease_and_reregister(
        inner: &std::sync::Arc<EtcdRegistryInner>,
        old_lease_id: i64,
        key: &str,
    ) {
        let re_grant = {
            let mut client = inner.client.lock().await;
            client
                .lease_grant(inner.config.etcd_lease_ttl().unwrap_or(15) as i64, None)
                .await
        };

        let Ok(current) = re_grant else {
            return;
        };

        let new_lease = current.id();
        inner.lease_id.store(new_lease, Ordering::SeqCst);

        let instance = ServiceInstance {
            addr: inner.config.rpc_self_listen_addr().unwrap_or_default(),
            metadata: HashMap::new(),
        };

        if let Ok(value) = serde_json::to_string(&instance) {
            let mut client = inner.client.lock().await;
            let opts = PutOptions::new().with_lease(new_lease);
            let _ = client.put(key, value, Some(opts)).await;
        }
        tracing::info!(old = old_lease_id, new = new_lease, "etcd lease renewed");
    }
}